Propeller for aircraft



Dec. 5, 1933. H. JUNKERS PROPELLER FOR AIRCRAFT Filed Dec. 15, 1931 2 Sheets-Sheet 1 /n venfor:

Mimi/km a;

Dec. 5, 1933. H. JUNKERS PROPELLER FOR AIRCRAFT Filed Dc.

15, 1931 2 Sheets-Sheet 2 In vemoe: 904 um/km Patented Dec. 5, 1933 UNITED STATES PATENT OFFICE PROPELLER FOR AIRCRAFT Hugo Junkers, Dessau, Germany Application December 15, 1931, Serial No. 581,185, and in Germany December 20, 1930 ,8 Claims. (Cl. 170-159) My invention relates to propellers, more especially for aircraft. It has particular reference to the blades of hollow metal propellers.

It is an object of my invention to provide a particularly simple, strong and readily produc-.

the blades and rigidly connected to the other parts of the blades for the absorption of centrifugal forces.

It has also been suggestedto form metal pro- 23 peller blades with two parts one of which is a casting having transverse ribs, longitudinal spars, 'and tension rods extending along the blade for bracing the casting while the other part is a metal sheath which isconnected to the casting by screws, rivets or the like, or by grooves in the casting and corresponding projections on the sheath.

A propeller blade which bears some resemblance to the last-mentioned type is described in my copending application for patent of the United States, Serial No. 545,511, filed June 19,

The blades referred to involve the drawback of being complicated in design, being'composed of a plurality of separate and separately manufactured members with a corresponding number of joints and other connections.

These drawbacks are eliminated according to the present invention and blades consisting of two parts are simplified by providing on the parts which may be cast, pressed or produced in some other suitable manner inwardly projecting ribs which engage each other, when the halves are connected, and make up any desired number of longitudinal spars, preferably merging into the shank of the blade. Preferably the leading and trailing edges of the blade are permanently connected by riveting, welding, soldering or the like, while the connection at the spars is detachable and may for instance be efiected by screws.

The tips of the blades are preferably solid portions at the outer ends of the parts, so that subsequent alterations of the propeller diameter are readily effected by machining the solid tips,

' spars, tensions rods or the like arranged within as described more fully in my said copending application. f

In the drawings aflixed to this specification and forming part thereof two types of propeller blades embodying my invention are illustrated diagrammatically by way of example.

In the drawings Fig. 1 is an elevation of a propeller blade having a single rib formed on' each part.

Figs. 2, 3 and 4 are sections on the corresponding line in Fig. 1,'drawn to alarger scale.

, Fig. 5 is an elevation of a propeller blade having two ribs formed on each part.

Figs. 6 and 7 are sections on the corresponding lines in Fig. 5, drawn to a larger scale, and Fig. 8 is a section on the axis of one of the screws for connecting the spars, drawn to a still larger scale, showing means for relieving the screw of shearing'forces.

Referring now to the drawings, and first to Figs. 1 to 4, the blade is composed of two halves a and b, preferably of light metal or alloy, which may be cast, pressed, or manufactured in any other suitable'manner. As best seen in Fig. 3, each part is formed with an inwardly projecting rib marked d for the part a and e for the part b. The inner faces of the ribs bear on each other and the ribs form together a longitudinal spar adapted to absorb forces. Near the inner end of the blade the two ribs or flanges merge into the preferably tubular shank c with V-shaped ends d and e'. The shank is secured in the boss of w the propeller (not shown) for instance, screwed into it.

As mentioned above, the leading and trailing edges of the blade are preferably connected in a permanent manner. In the present instance the permanent connection is effected by rivets g at the leading and trailing edges and by central rivets h, Fig. 2, at the tip 1 which is made solid in both parts, as and for the purpose specified. Obviously any other permanent connection, such as welding, soldering and the like may be provided instead of riveting. At "the ribs 11, e the parts a and b are connected by detachable means, screws 12 being shownby way of example.

Referring now, to Figs. 5-7 this blade is substantially similar to the blade described with reference to Figs. 1 to 4, with its spars a and I) connected .by'rivets g at the leading and trailing edges and central rivets h in the solid tip f, but here two parallel ribs 1', i and k, k are formed on the inner side of the respective parts a and b. Each rib is connected to its'mating rib by screws n, as best seen in Fig. '7. In this manner a tubular spar is obtained by which the blade is braced very efiiciently. The inner ends of the ribs constituting this tubular spar merge into the preferably tubularshank c as described with reference to Fig. 1, but here the merging is much more gradual on account of the tubular form of the spar, and the V-shaped portions e, d, Fig. 1, are dispensed with.

Referring now to Fig. 8, p is a ring which is inserted coaxially to-a screw n in circular grooves in the mating faces of ribs 11 and e for relieving the screw of shearing forces. Obviously similar means may be provided in connection with the screws for the ribs forming the tubular spar, Figs. 5-7, and in both cases may be provided for all screws or only for some of them.

I wish it to be understood that I do not desire to be limited to the exact details of construction which is arranged to bear on the corresponding.

rib of the other part, a permanent connection at the leading and trailing edges of the parts, a detachable connection at their ribs, and means for relieving the elements of said detachable connection of shearing forces.

2. A blade for hollow metal propellers com-' prising two parts adapted to be combined into a blade, an inwardly projecting rib on each part which is arranged to 'bear on the corresponding rib of the other part, a permanent connection at the leading and trailing edges of the parts, screws for connecting them at their ribs, and a ring arranged coaxially to each screw and inserted in grooves in the mating faces of said ribs for relieving said screws of shearingforces.

3. A blade for hollow metal propellers comprising two parts adapted to be'combined into a blade, an inwardly projecting rib on each part which is arranged to bear on the corresponding rib of the other part, a cylindrical shank at the inner end of said blade, and a V-shaped extension at the inner end of each rib, with its outer ends merging into the wall of said shank.

'rigid metallic shape of convex-concave configuration, a solid rib merging from the concave surface of each half and ending in the plane of division of the two halves, so that the ribs contact with each other when the two halves are superposed, and means for uniting said halves.

6. A hollow propeller blade comprising two superposed halves, each having the form of a rigid metallic shape of, convex-concave configuration, a solid rib merging from the concave surface of each half and ending in the plane of division of the two halves, so that the ribs contact with each other when the two halves are superposed, detachable connecting means extending across said ribs and permanently fixed connecting means uniting the longitudinal edges of said halves.

7. A hollow propeller blade comprising two superposed halves, each having the form of a rigid metallic shape of convex-concave configuration, a solid rib merging from the concave surface of each half and ending in the plane of division of the two halves, so that the ribs contact with each other when the two halves are superposed, detachable connecting means extending across said'ribs and permanently fixed connecting means uniting the longitudinal edges and the tips of said halves.

8. A hollow propeller blade comprising two superposed halves, each having the form of a rigid metallic shape of convex-concave configuration, two solid ribs merging from the concave surface of each half and ending in the plane of division of the two halves, the ribs of each half enclosing between them a semicylindrical cavity 'and contacting with the ribs of the other half, 

